In many devices it is necessary to measure two or more voltages. This measurement of two or more voltages may be effected for example by a microcontroller, which comprises a voltmeter for each voltage to be measured.
Thus, for example, when providing an electronic motor protecting switch for a three-phase electric motor, the three phase currents of the motor must be detected, for which purpose three independent voltmeters may be used in one microcontroller. For each further voltage to be detected, a further voltmeter would be needed in the microcontroller. However, microcontrollers with more than three voltmeters are more cost-intensive and are structurally larger than microcontrollers with only three voltmeters.